Media Compression Techniques

The JPEG Standard

JPEG(Joint Photographic Experts Group) is an image compression standard which was accepted as an international standard in 1992. Developed by the Joint Photographic Expert Group of the ISO/IEC JPEG is a commonly used method of lossy compression for digital photography (image) For coding and compression of color/gray scale images Yields acceptable compression in the 10:1 range The JPEG compression algorithm is at its best on photographs and paintings of realistic scenes with smooth variations of tone and color. For web usage, where the amount of data used for an image is important, JPEG is very popular. JPEG/Exif is also the most common format saved by digital cameras.

... but not so good at distinguishing the exact strength of a high frequency variation.JPEG Compression Process
Image Take 8x8 Pixel Blocks Discrete Cosine Transform Quantizer Binary Encoder . This is done by simply dividing each component in the frequency domain by a constant for that component. This allows one to greatly reduce the amount of information in the high frequency components.1011001. with
. and then rounding to the nearest integer Weights the various spectral coefficients according to their importance..
Quantization: The human eye is good at seeing small differences in brightness over a relatively large area.

JPEG encoding and decoding processes
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each entry in the original block falls in the range [0.255]
modified range is [
128.For an 8-bit image.127].
The DCT transforms an 88 block of input values to a linear combination of these 64 patterns
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Quantization Matrix
The quantized DCT coefficients are computed with
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animated GIFs contain multiple images which stream to create an animation effect. and can produce very large files. GIF images are compressed using the LempelZiv-Welch (LZW) lossless data compression technique to reduce the file size without degrading the visual quality
. An animated GIF can loop endlessly are not scalable.cont..
Though not technically movies.

The color limitation makes the GIF format unsuitable for reproducing color photographs and other images with continuous color.). but it is well-suited for simpler images such as graphics or logos with solid areas of color. It also supports animations and allows a separate palette of 256 colors for each frame. The colors are chosen from the 24-bit RGB color space.
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The format supports up to 8 bits per pixel thus allowing a single image to reference a palette of up to 256 distinct colors.

MPEG Audio basics
The MPEG compression methodology is considered asymmetric as the encoder is more complex than the decoder.[1] The encoder needs to be algorithmic or adaptive whereas the decoder is 'dumb' and carries out fixed Stereo audio streams contain largely redundant information MPEG audio compression takes advantage of these facts to reduce extent and detail of mostly inaudible frequency ranges
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It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission bandwidth.
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information".
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TV stations. MPEG-2 was the second of several standards developed by the Moving Pictures Expert Group (MPEG) and is an international standard (ISO/IEC 13818). cable. TV receivers.
MPEG-2 is widely used as the format of digital television signals that are broadcast by terrestrial (over-the-air). DVD players. It also specifies the format of movies and other programs that are distributed on DVD and similar discs. As such. and direct broadcast satellite TV systems. and other equipment are often designed to this standard.
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